Method of removing free halogen from a halogenated polymer insulating layer of a semiconductor device and resulting semiconductor device

ABSTRACT

A method is disclosed for removal of free halogen from a semiconductor device insulating layer, in particular, a halogen-containing polymer insulating layer. The free halogen is removed by contacting the insulating material with hydrogen ions under conditions which generate gaseous hydrogen halide which is then removed. A semiconductor device containing such treated insulating materials is also disclosed. The invention is particularly useful in removing free fluorine from fluorinated polymer insulating layers.

FIELD OF THE INVENTION

[0001] This invention relates to semiconductor device manufacturing.More particularly, the present invention is directed to a simplifiedmethod for removing free halogen, in particular fluorine, from ahalogenated polymer layer used as an insulating layer in a semiconductordevice.

BACKGROUND OF THE INVENTION

[0002] The integrated circuit manufacturing industry continuouslyprogresses toward more highly advanced and miniaturized integratedcircuits. With this progress toward smaller and smaller dimensions, thecapacitive loading of wiring levels has become a more and moresignificant problem. Traditionally, SiO₂ has been used to provideinsulation between conductive areas. In order to reduce the capacitanceof conductive areas, efforts have been made to use materials other thanSiO₂ to form insulating layers, that is, materials having a lowerdielectric constant than that of SiO₂. Various groups of materials havebeen identified and/or developed for this purpose, including varioustypes of halogenated polymers, such as fluorinated parylenes(paraxylylenes) and fluorinated polyimides. Fluorinated parylenes, andmethods of making them, are well known in the art (see, e.g., U.S. Pat.Nos. 5,268,202 and 5,879,808, the entireties of which are herebyincorporated by reference). Likewise, fluorinated polyimides, andmethods of making them, are well known to those skilled in the art.

[0003] In the manufacture of semiconductor devices, it is frequentlynecessary to form vias through such insulating layers, which istypically accomplished by any of a wide variety of etching techniquesknown in the art, e.g., reactive ion etching (RIE). In the case ofdamascene techniques, wherein trenches are formed in insulating layersand filled with conductive material, it is necessary to etch processingchannels for the wiring. It has been observed that when such etchingtechniques are applied to fluorinated polymers, free fluorine tends tobe produced. For example, a well known and preferred type of etchingtechnique for forming vias and/or trenches in insulating layers isreactive ion etching, e.g., using an oxygen plasma. When an oxygenplasma is used to form vias and/or trenches in a fluorinated polymersuch as fluorinated parylene, a majority of the free fluorine which isproduced exits the polymer in the form of F₂O, but some free fluorineremains in the fluorinated polymer. Such free fluorine cannot be removedusing oxygen plasma because such a treatment would cause furtheretching, thereby enlarging the etched areas beyond what is desired.Moreover, such further treatment would generate additional freefluorine.

[0004] Free fluorine produced in insulating layers can cause a varietyof problems in semiconductor devices, e.g., it can diffuse into andcontaminate other layers in the semiconductor device. Accordingly, inorder to use fluorine or other halogenated polymers as insulatinglayers, it would be desirable, and in some cases it would be necessary,to either remove the free halogen and/or block the free halogen fromdiffusing into other layers in which free halogen is undesirable ordeleterious.

[0005] Wang, et al., “Evaluation of TaNx and Al as Barriers to FluorineDiffusion from Fluorinated Parylenes” discloses barriers which aredesigned to prevent free fluorine from reaching sensitive areas withinsemiconductor devices.

[0006] U.S. Pat. No. 5,380,401 discloses a method of removing fluorinecontaminants from an aluminum-containing semiconductor bond pad,comprising exposing the bond pad to argon in a reactive ion etcher, andapplying energy to the argon.

[0007] There is a need for a method of easily and effectively removingfree halogen from insulating materials which contain such free halogen,e.g., free fluorine, without significantly adding to processing time orprocessing cost, and without etching or degrading the insulating layer,so as to avoid the need for adding a free halogen blocking layer to thedevice.

SUMMARY OF THE INVENTION

[0008] According to the present invention, there are provided simplemethods which, as discussed in more detail below, provide for effectiveremoval of free halogen from insulating materials which contain freehalogen, in particular, a halogen-containing polymer which has beensubjected to one or more etching techniques. The methods according tothe present invention achieve such free halogen removal and do notsignificantly add to processing time or processing cost, without etchingor degrading the insulating layer, thereby avoiding the need for addinga halogen-blocking layer.

[0009] According to one aspect of the present invention, there areprovided methods of removing free halogen from a halogenated polymer, bycontacting the halogenated polymer with hydrogen ions to generatehydrogen halide. The halogenated polymer is preferably contacted withthe hydrogen ions at a temperature and pressure at which the hydrogenhalide is gaseous. Alternatively, the temperature can be increasedand/or the pressure can be decreased following generation of hydrogenhalide to render the hydrogen halide gaseous.

[0010] There are further provided methods of forming semiconductordevices comprising contacting a free halogen containing insulatingmaterial layer of the semiconductor device with hydrogen ions.

[0011] In addition, there are further provided methods of formingsemiconductor devices comprising, applying an insulating layercontaining halogen onto a substrate, etching a pattern in at least theinsulating layer, thereby generating free halogen in the insulatinglayer, and contacting the insulating layer with hydrogen ions to convertfree halogen to hydrogen halide. The insulating layer is preferablyformed of a halogenated polymer.

[0012] There are also provided semiconductor devices formed as describedabove. Although the invention is applicable to any halogen containinginsulating layer, the invention is preferably used to remove freefluorine from a fluorinated polymer, preferably selected from the groupconsisting of fluorinated parylenes and fluorinated polyimides.

[0013] These and other features and advantages of the invention willbecome more readily apparent from the following detailed description ofpreferred embodiments of the present invention which is provided inconjunction with the accompanying drawings. The invention is not limitedto the exemplary embodiments described below and it should be recognizedthat the invention includes all modifications falling within the scopeof the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a diagrammatic sectional view of a plasma reactor whichis suitable for use in carrying out methods according to the presentinvention; and

[0015]FIG. 2 is a diagrammatic side elevational view of the plasmareactor depicted in FIG. 1.

[0016]FIG. 3A is a cross-sectional view of a substrate according to anembodiment of the present invention.

[0017]FIG. 3B is a cross-sectional view of the FIG. 3A structure at alater stage.

[0018]FIG. 3C is a cross-sectional view of the FIG. 3B structure and alater stage of processing.

[0019]FIG. 3D is a cross-sectional view of the FIG. 3C structure at alater stage of processing.

[0020]FIG. 3E is a cross-sectional view of the FIG. 3D structure at alater stage of processing.

[0021]FIG. 4A is a cross-sectional view of a substrate according to asecond embodiment of the present invention.

[0022]FIG. 4B is a cross-sectional view of the FIG. 4A structure at alater stage of processing.

[0023]FIG. 4C is a cross-sectional view of the FIG. 4B structure at alater state of processing.

[0024]FIG. 4D is a cross-sectional view of the FIG. 4C structure at alater stage of processing.

[0025]FIG. 4E is a cross-sectional view of the FIG. 4D structure at alater stage of processing.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0026] As mentioned above, a first aspect of the present inventionrelates to removing free halogen from a material to be used as aninsulating layer in a semiconductor device. The insulating layer inaccordance with this aspect of the invention is preferably a halogenatedpolymer.

[0027] In a second aspect of the present invention, there is provided amethod of removing free halogen from a halogenated polymer.

[0028] Preferred materials for use as the insulating layer of the firstaspect of the present invention or the halogenated polymer of the secondaspect of the present invention include halogenated parylenes andhalogenated polyimides, with the preferred halogen being fluorine. Thoseof skill in the art can readily manufacture halogenated parylenes andhalogenated polyimides using techniques known in the art. The paryleneand/or polyimide used in accordance with the present invention ispreferably halogenated substantially to the maximum possible extent,i.e., all hydrogen atoms are preferably replaced with halogen atoms. Itis preferred that all such substitutions be with fluorine, although itis possible to use other halogens (in particular, chlorine, bromine oriodine) and/or combinations of halogens. In addition, the presentinvention covers any other suitable halogenated polymers, includingparylenes and polyimides in which some of the mers are substituted withsubstituents other than halogens, so long as at least some of the mersare substituted with one or more halogen in at least one position.

[0029] According to the present invention, free halogen in the materialto be used as an insulating layer, e.g. a halogenated polymer, isremoved by contacting the material with hydrogen ions to generatehydrogen halide. The insulating material and/or the halogenated polymeris preferably contacted with the hydrogen ions at a temperature andpressure at which the hydrogen halide is gaseous.

[0030] In preferred cases, the free halogen is fluorine and theinsulating material and/or the halogenated polymer is contacted withhydrogen ions. The boiling point of hydrogen fluoride (HF) atatmospheric pressure is about 19.4° C. Hydrogen plasma reactions aretypically conducted under sub-atmospheric pressure conditions.Accordingly, ambient temperature conditions are usually sufficient togenerate gaseous HF in such cases, and such HF readily can be ventedfrom the insulating material. The temperature surrounding the materialfrom which free halogen is being removed can be elevated to increase therate of reaction. For example, the surrounding temperature canpreferably be elevated to at least about 100° C.

[0031] Alternatively, the material from which free halogen is beingremoved can be contacted with hydrogen ions under conditions at whichthe hydrogen halide which is generated is not gaseous, and then thetemperature can be increased and/or the pressure can be decreasedfollowing generation of hydrogen halide to render the hydrogen halidegaseous.

[0032] Those of skill in the art can readily recognize that a widevariety of conditions could be employed to achieve the functions of thepresent invention. For instance, the pressure in the environmentsurrounding the material from which free halide is being removed (i.e.,the insulating material and/or the halogenated polymer) during contactwith hydrogen ions can be lower or higher than atmospheric pressure, andthe temperature can be selected such that the hydrogen halide isgaseous. In addition, it is possible to generate hydrogen halide underconditions at which the hydrogen halide is not gaseous, and later alterthe conditions to render the hydrogen halide gaseous.

[0033] The hydrogen being used to form hydrogen halide with the freehalide is preferably ionized either as it contacts the insulating layerfrom which free halide is being removed, or prior to contacting theinsulating layer.

[0034] A suitable way to generate hydrogen ions is through the use of alow pressure plasma reactor. A representative example of such a deviceis shown in FIGS. 1 and 2. FIGS. 1 and 2 depict a suitable plasmareactor apparatus 10 for use in accordance with the present invention.The plasma reactor apparatus 10 comprises an electrically insulativeshell 12 having internal walls 14. The walls 14 define an internalreactor cavity 16. An example of a suitable material for construction ofthe shell 12 is quartz. Electrically conductive inductive coils 18 arepositioned externally of the cavity 16 and the shell 12, and wraptherearound. The inductive coils 18 constitute an inductive couplingmeans positioned externally of the cavity 16 for inductively generatingand transmitting electromagnetic radiation into the reactor cavity 16 toionize gases therein into a plasma state. The coils 18 are powered by asuitable conventional power supply 20. A representative example of asuitable power supply is 13.56 MHz and 3000 watts. An internal electrode22 is provided for supporting a workpiece 23, i.e., the material beingtreated (in the present embodiment, the workpiece is a semiconductorwafer). The internal electrode 22 is as well connected to a conventionalcapacitively coupled bias power source 24 which could be used foranisotropic etching. A capacitive coupling plate 26 is positionedexternally of the cavity 16 and the shell 12, intermediate the cavity 16and the inductive coils 18. A capacitive coupling plate 26 is connectedvia a conductive line 28 to a switch 30. The switch 30 is operable toconnect the plate 26 to one of a ground source/potential 32 or a powersource 34. The power source 34 can suitably be configured for operatingat a frequency from 100 KHz to 60 MHz. The plate 26, the line 28, theswitch 30 and the power supply 34 comprise a capacitive coupling systempositioned externally of the cavity 16 for capacitively generating andtransmitting electromagnetic radiation into the reactor cavity to ionizegas therein into a plasma state, and for drawing plasma ions in thedirection of the plate 26 system. Such provides but one example of acapacitive coupling system. Others, of course, would be also suitable.For example, a capacitive coupling system could be provided wherein theplate 26 is positioned other than intermediate the cavity 16 and thecoils 18.

[0035] The plasma reactor described above is merely one example of aplasma reactor which could be used in practicing the present invention,and those of skill in the art will recognize that any reactor whichwould be suitable for generating. hydrogen ions would be suitable foruse in accordance with the present invention.

[0036] The hydrogen ions are preferably substantially the only materialcontacting the material from which free halide is being removed,although it is possible for other materials to be present (i.e., otherthan the hydrogen halide being formed). If other materials are present,such other materials preferably do not substantially etch the materialfrom which hydrogen halide is being removed.

[0037] The above-described techniques are simple methods which providefor effective removal of free halogen from materials which contain freehalogen, in particular, halogen-containing polymer which has beensubjected to one or more etching techniques. The methods of the presentinvention achieve such free halogen removal without significantly addingto processing time or processing cost, and without etching or degradingthe insulating layer.

[0038] The present invention is further directed to methods of formingsemiconductor devices comprising applying an insulating layer containinghalogen onto a substrate, etching a pattern in the insulating layer,thereby generating free halogen in the insulating layer, and contactingthe insulating layer with hydrogen ions to convert free halogen tohydrogen halide.

[0039] A representative embodiment of a method of forming asemiconductor device according to the present invention is depicted inFIGS. 3A-3E.. Those of skill in the art will recognize that thesemiconductor device shown in FIGS. 3A-3E is only one example ofsemiconductor devices which can be made according to the presentinvention, and that the present invention is applicable to any typesemiconductor device containing a halogenated insulating layer in whichfree halogen is produced during semiconductor fabrication. Thus, theremay be numerous integrated circuit device structures below and/or abovethe insulating layer illustrated in FIGS. 3A-3E, but since the inventioncan be applied to any semiconductor device, only the layers affected bythe present invention are being described and illustrated.

[0040] In addition, the expression “layer” is used herein to refer toeither a single stratum or a plurality of strata. In other words, thoseof skill in the art are familiar with the fact that a stratum having oneor more particular features (e.g., composition) can be replaced with aseries of strata which provides a similar function.

[0041] Furthermore, the expression “substrate” is used herein to referto either a single layer, or one or more layers of materials on a baselayer.

[0042]FIG. 3A is a cross-sectional view of a substrate 60. The substrate60 can be any suitable substrate, and can be formed according to any ofthe various methods known for forming a substrate. It may be a layer ofsilicon, or it may be formed by a plurality of material layers and mayalso contain portions of or complete electronic devices fabricated inthe substrate.

[0043] An insulating layer 61 is applied to the substrate 60. Asmentioned above, the insulating layer 60 is formed of a halogenatedpolymer, such as a fluorine containing polymer. The step of applying ahalogenated polymer can be conducted in any suitable manner, e.g. spincoating, depending on the nature of the halogenated polymer. Thehalogenated polymer is preferably cured (or allowed to cure) beforefurther processing. FIG. 3B is a cross-sectional view of a laminate ofthe substrate 60 and the insulating layer 61.

[0044] At least one via is etched in the insulating layer 61. Theetching can be conducted in any suitable manner, numerous types ofetching being known in the art and being suitable. As mentioned above, apreferred example of a suitable etching method is by reactive ionetching, most preferably, using an oxygen plasma method. As mentionedabove, oxygen plasma etching (as with any other type of etching) causesthe generation of free halogen, but also eliminates a significant amountof the thus-generated free hydrogen in the form of oxide of the halogen,e.g. F₂O. FIG. 3C is a cross-sectional view of the laminate of FIG. 3Bwhich has been etched according to the third embodiment of the presentinvention, this view showing a via 62. The FIG. 3C structure is thencontacted with hydrogen ions as discussed above to produce hydrogenhalide. The insulating material and/or the halogenated polymer ispreferably contacted with the hydrogen ions at a temperature andpressure at which the hydrogen halide is gaseous. Alternatively, aftercontact of the halogenated polymer with hydrogen ions the temperatureand/or pressure can be adjusted to form gaseous hydrogen halide.

[0045] Next, a conductive material is deposited into the via 61. FIG. 3Dis a cross-section view of the laminate of FIG. 3C which includes aconductive material 63 deposited in the via 62.

[0046] The structure of FIG. 3D can then be subject to furtherconventional fabrication steps to produce an operative semiconductordevice.

[0047] The invention may also be used to produce multi-layerinterconnects in semiconductor devices, as illustrated in FIGS. 4A-4E.

[0048]FIG. 4A illustrates a semiconductor substrate 50 which as in theprior embodiment, may include numerous material layers forming portionsof or cp,[;ete electronic devices. As shown in FIG. 4B a conductor layer51 is applied on substrate 50. This may be a patterned interconnectlayer for a semiconductor device. Next, as shown in FIG. 4C ahydrogenated polymer insulating layer 52 is applied, cured and thenetched, as shown in FIG. 4D to form vias 54. This structure is thensubject to hydrogen ion contact to remove free halogen and generatehalogen halide in the manner described above with reference to FIG. 3C.Then, as shown in FIG. 4E a conductive layer 53 is applied to fill inthe vias 54, and the FIG. 4E structure can be further fabricated inconventional manner to produce an operative semiconductor device.

[0049] The present invention is suitable for use in the manufacture ofany kind of semiconductor device, e.g., a microprocessor, logic device,DSP, memory device etc.

[0050] The present invention is further directed to any sequence ofprocess steps which includes performance of any of the processes inaccordance with the present invention, in addition to any other processsteps, including but not limited to coating or applying one or moreadditional layers, removing part of all of one or more additionallayers, creating a pattern on a surface of a layer by applying, exposingand developing a photoresists and then removing portions of the layerdefined by the pattern, forming interconnect holes through two or morelayers, creating interconnects, etc.

[0051] As noted, the hydrogenated polymers with which the invention ispreferably used are fluorinated parylenes and fluorinated polyamides inwhich case the removed free halogen is fluorine.

[0052] Although articles and methods in accordance with the presentinvention have been described in connection with preferred embodiments,it will be appreciated by those skilled in the art that modificationsnot specifically described may be made without departing from the spiritand scope of the invention. Accordingly, the invention is not limited bythe foregoing description, but is only limited by the scope of theappended claims.

What is claimed is:
 1. A method of removing free halogen from ahalogenated semiconductor insulator, comprising contacting saidinsulator with a material which reacts with free halogen in saidinsulator under conditions which generate gaseous halogen components,and removing said gaseous halogen components.
 2. A method as in claim 1where said insulator is a polymer.
 3. A method as in claim 2 where saidmaterial is hydrogen.
 4. A method as in claim 3 where the hydrogen ispartially or completely ionized.
 5. A method as in claim 4 where thehydrogen is ionized prior to its contact with a surface of said polymer.6. A method as in claim 2 where the temperature during or subsequent tosaid hydrogen contact is above 20° C.
 7. A method as in claim 2 wheresaid halogen is fluorine.
 8. A method as in claim 7 wherein said polymeris a fluorinated polyimide.
 9. A method as in claim 7 where said polymeris a fluorinated parylene.
 10. A method as in claim 4, wherein saidhydrogen ions are generated by a hydrogen plasma.
 11. A method as inclaim 1, wherein said halogen is selected from the group consisting offluorine, chlorine, bromine and iodine.
 12. A method as in claim 6,wherein said contacting is conducted at a temperature of at least about100 degrees C.
 13. A method of removing free halogen from halogenatedpolymer, comprising: contacting said halogenated polymer with hydrogenions to generate hydrogen halide; and causing said hydrogen halide to begaseous.
 14. A method as in claim 13, wherein said hydrogen ions aregenerated by a hydrogen plasma.
 15. A method as in claim 13, whereinsaid halogen is selected from the group consisting of fluorine,chlorine, bromine and iodine.
 16. A method as in claim 15, wherein saidhalogen is fluorine.
 17. A method as in claim 15, wherein saidhalogenated polymer is selected from the group consisting of fluorinatedparylenes and fluorinated polyimides.
 18. A method of making asemiconductor device, comprising: contacting a free fluorine containinginsulating layer of said semiconductor device with hydrogen ions, underconditions such that at least a portion of said free fluorine isconverted into gaseous hydrogen fluoride.
 19. A method as in claim 18,wherein said hydrogen ions are generated by a hydrogen plasma.
 20. Amethod as in claim 18, wherein said insulating layer is formed of afluorinated polymer.
 21. A method as in claim 20, wherein saidfluorinated polymer is selected from the group consisting of fluorinatedparylenes and fluorinated polyimides.
 22. A method as recited in claim18, wherein said contacting is conducted at a temperature above 20° C.23. A method of making a semiconductor device, comprising: contacting afree fluorine containing insulating layer of said semiconductor devicewith hydrogen ions under conditions such that at least a portion of saidfree fluorine is converted into hydrogen fluoride; and increasing thetemperature and/or decreasing the pressure in an environment surroundingsaid insulating layer to render said hydrogen fluoride gaseous.
 24. Amethod as in claim 23 wherein said hydrogen ions are generated by ahydrogen plasma.
 25. A method as in claim 23, wherein said insulatinglayer is formed of a fluorinated polymer.
 26. A method as in claim 25,wherein said fluorinated polymer is a fluorinated parylene.
 27. A methodas in claim 25 where said fluorinated polymer is a fluorinatedpolyimide.
 28. A method of making a semiconductor device, comprising:applying an insulating layer containing fluorine onto a substrate;etching a pattern in insulating layer, said etching generating freefluorine in said insulating layer; contacting said insulating layer withhydrogen ions under conditions such that at least a portion of said freefluorine is converted to gaseous hydrogen fluoride; and, removing saidgaseous hydrogen fluoride.
 29. A method as in claim 28, wherein saidhydrogen ions are generated by a hydrogen plasma technique.
 30. A methodas in claim 28, wherein said insulating layer is formed of a fluorinatedpolymer.
 31. A method as in claim 30, wherein said fluorinated polymeris a fluorinated parylene.
 32. A method as in claim 30 wherein saidfluorinated polymer is a fluorinated polyimide.
 33. A method as in claim28, wherein said contacting is conducted at a temperature greater than20° C.
 34. A method as in claim 28 wherein said contacting is conductedat a temperature and pressure at which said hydrogen fluoride isgaseous.
 35. A method of making a semiconductor device, comprising:applying an insulating layer containing fluorine onto a substrate layer;etching a pattern in said insulating layer, said etching generating freefluorine in said insulating layer; contacting said insulating layer withhydrogen ions to convert at least a portion of said free fluorine tohydrogen fluoride; increasing the temperature and/or decreasing thepressure in an environment surrounding said insulating layer to rendersaid hydrogen fluoride gaseous; and removing said gaseous hydrogenfluoride.
 36. A method as in claim 35 wherein said hydrogen ions aregenerated by a hydrogen plasma.
 37. A method as in claim 35, whereinsaid insulating layer is formed of a fluorinated polymer.
 38. A methodas in claim 37, wherein said fluorinated polymer is a fluorinatedparylenes.
 39. A method as in claim 37 wherein said fluorinated polymeris a fluorinated polyimide.
 40. A semiconductor structure comprising: asubstrate; and an insulating layer on said substrate, said insulatinglayer containing a halogen and having a surface which has been treatedto remove free halogen therefrom.
 41. A semiconductor structure as inclaim 40 wherein said halogen is fluorine.
 42. A semiconductor structureas in claim 40 wherein said surface was treated with hydrogen ions. 43.A semiconductor structure as in claim 41 where the insulator is afluorinated polymer.
 44. A semiconductor structure as in claim 43wherein said polymer is a fluorinated parylene.
 45. A semiconductorstructure as in claim 43 wherein said polymer is a fluorinatedpolyimide.
 46. A semiconductor device comprising: a substrate containingsemiconductor features; and a fluorinated polymer layer covering saidsubstrate, said fluorinated polymer layer having had free fluorine atomsremoved therefrom by a contact of said fluorinated polymer layer withhydrogen ions.
 47. A semiconductor device as in claim 46, wherein saidsemiconductor device is a memory device.
 48. A semiconductor device asin claim 46, wherein said fluorinated polymer is a fluorinated parylene.49. A semiconductor device as in claim 46 wherein said fluorinatedpolymer is a fluorinated polyimide.